Automatic telephone system



.-25' 1927. 'A. B. PREUSS AUTOMATIC TELEPHONE SYSTEM 7 Filed Aug. 21, 1925 5 Sheets-Sheet Q 1W HZEXandEr Brunu Frauss A. B. PREUSS AUTOMATIC TELEPHONE SYSTEM Oct. 25, 1927.

Filed Aug. 21, 1925 Invenlur Filexandsr Brunt] Freuss HIT'H:

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5 Sheets-Sheet 3 5 w r E F Fur. an. 0 O o n gm v m r Em v E is}... E 0 fi uo ono wm o d on" H H Q: wu fxm m 0 w y ll. fi E @J wk mm M Wm an.

A. B.'PREuss AUTOMATIC TELEPHONE sYsrEu Fild Aux. 21, 1925 N NN o O 0 H0 0 v QQQ QM NR\ Q5 ATE I Q;

Ill-m Oct; 25 1927.

f E T rl M.

W E N. NE QM Q XJ n 25 1927. Oct A. B. PREUSS AUTOMATIC TELEPHONE SYSTEM" 5 Sheets-Sheet 5 Filed Aug. 21, 1925 c lf V filexandar Bruno Freus 1% 2 w in Q3 k o Qh/WQI o K N? as; k U J. u

Patented Oct. 25, 1927. I I v UNITED STATES} rat-rea since.

ALEXANDER BRUNO PREUSS, OF BERLIN-CHARLOTTENBIT3G, GERMANY, ASSIGNOR TO SIEMENS & HALSKE AKTIENGESELLSCHAFT -WERNEB'WERK, F filEMENSSTADI. BE]: BERLIN, GER-MANY.

AUTOMATIC TELEPHONE SYSTEM.

Application filed August 21, 1925, Seria1 No. 51,616, and in Germany September 27, 1924.

The present invention relates to automatic L1. If, for example, a subscriber T1 wishes telephone systems, especially to. those in to make a call to any particular subscriber which calls are set up over several exchanges of the exchange V, a final selector LVVI is connected in series. taken into use over his preselector VW'l and In the known arrangements of thiskind the final selector is raised to the fifth level, the setting up of connections over several from which there is a group of outgoing exchanges connected in series is etlec ted trunk lines to the exchange V. Only, the either by means of so calledthrough going lines L1 and L5 or this group are shown. so traliic, that is, each exchange calls the suc- As soon as the final selector Ll Vl has found 1o ceeding exchange and is then switched an idle trunk llHQIOTQXEUDPlG L1, the final through to the next exchange or the setting selector Ill V5 at the exchange V is taken up is effected byrunning a trunk-line through into use over the lineLlI, the contacts 1 all the exchanges and by providing a special and 2 of the repeater Ueh and the line L111 o jack in each of the exchanges located in seoiithe exchange II, the contacts 3 and 4 of rics foreach connection from one exchange the repeater U62, and the line LlIII oi the to the next. Y exchange III, contacts 5 and 6 of the re- Now the object of the present inventionis peater U63, and the line ,LlIV of the ex to enable calls between the individual eX- change IV, and over the preselecto-r VNo 70 changes located in series to be set up in an to the final selector LVN). In th manner entirely automatic manner in both directo be hereafter more fully described, the contions, and to render the plant as economiacts oi? the final selectors LIVQ, LN3 and cal as possible by simultaneously using each LW4l, to which the trunk line Ll isaccessi trunk line for different calls. According to ble are. marked engaged, so that the trunl; 75 the invention, this is achieved by running line Ll can no longer be taken into use.

the trunk lines. which are subdivided into If a. subscriber or the exchange V be groups, over all the exchanges located in wanted by the subscriber T2 of the exchange series, and by rendering each of the can II, the preselector VlVQ hun s an d e changes accessible from all the other 911- final selector such as LWQ, which is set onto so changes only over a particular trunk line or e fifth level and takes into use an idle group of trunk lines. At the individual extrunlrlineto the exchange V, for example, changes, these trunk lines are provided with the line L111. From the-line LlII, this conswitchingover d i hi h di onn t it nection follows the same route as that de section of the trunk line when this section scribed for the subscriber T1. The open- 5 is taken into use, and render the idle section 11g Oi the contact 2 prevents this trunk lin availaliile tor the traflic between other exbeing taken into use from the exchange I,

Chang-6S while another connection can be setup from B way f example, the figures sho diathe exchange II, to the exchange I over the.

gmmmatalcany Circuit arrangement for section L11 of the trunk line L1 and over so five automatic exchanges located in series. the preselectol' VVW Over Contact in s" 40 The Fig. 1 shows a fundamental circuit for Working position.

the whole arrangement, while the Figs, 2 It the line L1 be taken into use by asuband 3 show the circuit of a trunk line, over Scribcr T3 of the exchange III ove he picwhich the two end exchanges can be selectori lVl and the final selector Ill V3, the

reached, and the Figs. l and 5 show the cirline L1 is disconnected at the contact 4, so cuit of a trunk line, over which a connection th t a Connection can be set up from the can be setup. with a particular intermediate X hal ge II or III to the exchange I over exchanga the hne sections, L11 or LlII and L11 over The method of operating the whole arcontacts lor 3, in its working pos ition,.re- .ioo

rangement will now he described in detail spectively, in addition to the connection e 5 with reference to the diagrammatic circuit tending Over the Sections LIIII, and L'lIV (Fig. l). The exchanges I and V can be to the exchange V. In a similar manner it reached by all the exchanges over the line is possible for calls to beimade simultaiie ously between the exchange IV and the exchanges V and I.

T he same kind and number of calls can be set up over the line L5, which likewise serves to set up connections to the end exchanges I and V. For example, connection can extend from the subscriber T5 of the exchange V over the preselector VIVS, the final selector Ill V5 in the first level, the line L5IV, contacts 7 and 8 of the repeater U64, line LSIII, contacts Qand 10 of the repeater U65, line L5H, contacts 11 and 12 of the repeater U66, line L51, and over the preselector V V8 to the final selector LIVl of the exchange I. The other connections from the separate intermediate exchanges II to IV to the two end exchanges I and V or from the exchange I to the exchange V extend in the same manner as that previously described above for the line L1, so there is no need to describe them in detail.

Only the exchange II can be reached over the line L2, while only connections to the intermediate exchanges III or IV can be set up over the lines L3 or L4, respectively, if,

for example, the subscriber T1 of the exchange I wishes to make a call to a subscriber of the exchange II, a trunk line L2 is taken into use over the preselector V WI and the, iinal selector LVVl in the second level, this line going over the contact 13 ot the repcater U67 to the preselector VVVQ of the exchange II. The contact 14 is operated when the repeater U67 is taken into use, hence a call incoming from one o1 the succeeding exchanges III to V over the line section L2H is taken to the preselector VI /1O. A full description will be given hereafter oi the manner in which a call is switched from one of the succeeding exchanges, and how the line L2 is prevented from being taken into L3 at the contact 16 trunk line L3II is taken into use.

lcctor VWZ and over use.

If a subscriber of an exchange I, II,.IV, or V wishes to set up a call to a subscriber of the exchange III, for example, the subscriber T2 belonging to the exchange II, the line L3H is taken into use over the presethe 'final selector LIVQ set on the third level. This line extends over contact 16 oi. repeater U610 in its working position, over the contact of the repeater Ucll and to the preselector VlVll at the exchange III. The disconnection of the line prevents the line being taken into use by a final selector of the exchange I, while the line section L3III is switched over at contact 17 to the preseleo tor V'W12 of the exchange III when the Hence a connection set up from the exchange IV or V to the exchange III extends over the line sections LSII'I or LSIII and L3IV respectively, through the repeater U612 to the preselector VW12. y

The exchange IV can only be reached over of trunk lines.

oil-normal contact 761,

a group of trunk lines represented by the line Lat. For example, if the subscriber T2 of the exchangeII wishes to set up a call to the subscriber of the exchange IV, the connection extends over the preselector VIVQ, the final selector LIVE, the line IAII, which is connected tothe fourth level, overcontact of repeater U615 in its working position, over the contact 18 of the repeater U613, the line L4III, contact 19 of the repeater U614, and over the preselector VlVlS to the final selector LIVt, to which the wanted subscriber of the exchange IV is connected. At the contact 20, the trunk line L l is divided, so thatit cannot be taken into use by the ex change I over the line IAI and the repeater U615. The contact 21 is operated when the repeater U614 is taken into use, hence the exchange IV can still be reached by the ex change V over the line IAIV, the contact 21, and overthe preselector VVV 14:-

It remains to be mentioned that the exchanges are shown provided only with final selectors, so that :for the local traflic each exchange can have only subscribers lines. This, however, is only shown in the example for the sake of simplicity. It is'ob-viou's that the groups of trunk lines, of which the trunk lines L1 to L5 are shown, could also be connected to the bank contacts selectors in the different exchanges, so that these could contain as many subscribers lines as desired. 6 i

The Figs. 2 to 5 show in detail the circuits of two trunk lines, each in a separate group Thus the Figs. 2 and 3 show the circuit of the trunk line L1, while the Figs. 4 and 5 show the circuit of the trunk line L3. V

The inethod of operating the circuit in rangeinent for trunk lines to the end exchanges I and V will nowbe described in detail with reference to the Figures 2. and 3. For this purpose it will be assumed that the subscriber T1 wishes to set up a call to a subscriber of the exchange V. When the receiver is lifted down at the instrument of the subscriber T1, the presclector VlV 1 is started in known manner over the leads a and I), and the preselector selects an idle final selector such as LIVl. As soon as this is found, the relayT is operated over its wind ings I and II and 'overthe test wiper of the presclector in series with the relay C ofthe iinal selector LIVl. This circuit containsthe oi the final selector, which is closed only when the final selector is in its normal position. The relay T opens the rotary magnet circuit of the preselector VIVl in the known manner; at its contacts t1 and 52, it connects the subscribers leads a and 5 through to the leads a1 and 61 of the final selector LVVl; and at its contact 153, it short circuits its high resistance winding I, thereby put-ting the engaged condition on the.

final selector taken into use in known manner. At the same time, the relay R is operatcd over its windings 1 and 11 and the subscribcrs loop a, b. At the contactrl a circu-it is closed for the slow acting relay V1,

Cri

which at its contact all prepares the circuit for the lifting magnet H through the winding of the relay VB and the wiper 81 ot the side switch. The first train of impulses transmitted by the subscriber T1 comprises 5 current impulses. The relay R falls back a number of times corresponding to the number of impulses transmitted, and each time closes, at its back contact 12, the circuit for the lifting magnet H, which has been premagnet H raises the wipers of the final se-. lector LlV to the fiithlevel, in response to the selected number 5, whereupon, at the end of the train of impulses, the relay VB falls back and opens at its contact W1 the circuit of the side switch magnet S, so that the side switch is moved on into position 2.

The calling subscriber now transmits one current impulse for the purpose of initiating the non-numerical selection of atrunk line connected to the fifth level. The relay R again falls back and energizes the rotary magnet 1) over'the contact T2 and over the contacts 011. and p1, the winding 01' the relay VR and over the side switch arm at in position 2. The wipers LVVl are set onto the first contact on the fifth level. The multiple contacts mic close upon the first rotary step on level 5 (and also on levels 2 to 4,

inclusive). The wipers continue in theirrotary motion it the line connected to this contact be engaged, this being effected by'the further energization of the rotary magnet D over the multiple contact ml" and the interruptcr until a tree trunk line, for example L11. has been found. Thereupon the relay P1 is energized in the following circuitz earth, winding of P1, contact 01, test wiper of relay LVl, lead 02, home position contact of the test wiper of VVVT, windings 11 and 1 of T11, battery, earth. At its contact 201, the relay P1, opens the rotary magnet circuit, whereupon the switch is stopped, and

at its contacts 792 and p3 it switches through the leads a1 and 61 over condensers to the leads L11a and L11?) of the trunk line L1 taken into use. The relay VR, having operated again, falls baclg-the magnet S is deener-gized and the switch wipers are allowed to' move into position 3. The relay Ur is also energized over the contact W2 and the oft-normal contact 702'. The relay UR, at its contact rl, connects the interrupter U to the contact 3 of the side switch, therebymomentarily energizing the magnet S, which moves the side switch into position 4.

The relay T11 of the preselector VVV'Y, which was energized when the trunk line L11 was taken into use, at its contacts U11 and 2611, disconnects the windings I and 11 of the relay R2 from the leads a2 and Z22 go ing to the preselector VVY, and at its con tact 3t11, applies earth to the third lead L110 of the trunk lire L11. The relay'Ul oi the repeater U01 of the exchange 11 is there by energized over the contacts t11 and M21. The relay U1, at its contact M11, opens the test circuit of line M7, 67 connected to the contacts of the final selectorLW2, hence the trunk line L1 cannot be taken into use by the exchange 11. At the contacts e12 and 73 in the final selector LX1 1, a circuit is closed for the relay A1 of the repeater U01 over the following route: earth, contact 021, L

winding 11 of A1, contact t13, lead L117), wiper of LW1, contacts 793, 23, 4212, p2, lead 1111a, contact 2512, winding 1 01. A1, contact 022, battery, earth. The relay A1, at its contact (e11, closes a circuit over theback con- It tact-023 for the winding of the relay C1,

. which, at its contacts cll-and 012, disconnects the windings 1 and 11 of the relay A2 from battery and earth, and connects these windings in series with'the contact 0 12, across the outgoing leads L111a and L111b. A circuit is thus prepared for the transmission of current impulses to the repeater U02 at the .exchange 111. The relay U1,at its contact M12 and over the contact 2521, applies earth to the lead L1110 going to the exchange 111, and energized the relay U3 at the repeater 1162 over the contacts 2531 and M41. The re lay U3 then energizes the relay U5 at the repeater U63 in the exchange 1V over the contact M31 and the contact 2541-2 and over the lead L111I0 and the contacts 51 and M61.

When the relay C1 operates at the repeater U01, the contact 013 opens the test circuit of the branchot the trunk line L1, which goes to the final selector L1V2. The trunk line is thus also marked engaged to other calls in the direction of the'end exchange 1.

Therelay A3 of the repeater U02 -i.s energized in series with the windings 1 and 11 the leads LlIIa and L111?) by means of the contact (212. This circuit extends from earth at the contact 0 11 at the repeater U62 through the winding 11 of A3, contact .2532, lead 1 1111), contact $23, winding 11 of the relay A2, contacts "012, 2212, 011, winding 1 of A2, contact t22, lead 1411141,, contact of the relay A2, which are bridged'across &

Winding I of A3, and over the contact 042 to battery andearth. At contact (431, the slow acting relay C3 is energized over the back contact (:43 and the-relay, at its contact 033, interrupts the test circuit of the branch of the line L1, which is connected to the first level of the final selector LVV3. When the relay U3 operates, its contact @031 interrupts the test circuit for the branch of the line L1 going to the exchange V via the final selector Ill V3. The relay C3,at its contacts 031 and 032, disconnects the windingsI and II of the relay A l from battery and earth and connects them across the leads LlIIIa and LlIIIZ) in series with the contact e32; at its contact 034-, the relay prepares a. circuit for the relay V 4-; and at its contact 035, it disconnects the winding of the relay O4 from the contact (lll in order to prevent the operation of the relay C4.

"In a similar manner the preparation of the repeater U63 for the repetition of the current impulses over the branch ofthe line L1 as well as the marking engaged of this trunk which is accessible to the final selector LVV l is effected, For the sake of simplicity,

the circuit of the repeater U03 is not shown in full, because all its details correspond to The those of the repeater U61 and U02. leads LlIVa and IJlIVb, which are connected to the leads of the preselector VIVG, are bridged at the repeater U63 by a relay corresponding to the relay A4. Hence, the relay R3 at the preselector VIVG in the ex- 7 change V is energized and causesthe preselector to be set in motionand take into use an idle final selector in the exchange V such as LWV5. Then the test wiper of VlV 6 leaves its normal position, it opens the test circuit of theoutgoing line branch IJlIV marking this engaged to the outgoing trafiic. As soon asthe calling subscriber transn'iits the next train of impulses, Which, in i the present example, corresponds to the tens digit of the wanted subscribers number, the relay R at the final selector LWVl falls back a number of times, corresponding to the number of impulses transmitted, and at each impulse opens, at its contact 93, the circuit of the windings I and II of the relay A1. Relay A1 releases at each impulse and, at its contact all, closes a circuit for the relay V2 over the contact 015, and opens its contact e12. The slow acting relay V2 operates and remains attracted for the duration of the train of impulses. In order to improve the repetition of the currentimpulses, the windings of the relay A2 are short 'circuited over the contactsc2l and e22 duringthe impulse period. At each impulse, the relay A1, at its contact (112, opens the circuit of the relay A3, which energizes the relay A4 over the contact Q31 and the contact 043. The windings of the relay A l are short circuited over the contacts M1 and 4142 during the im- ,means of the magnet M the final pulse period. At its contact 0432 the relay A3 opens the circuit of a repeating relay, corresponding tothe relay A3, and located at the repeater U63. 7 over the contacts 2242 and 2543, Z53 and $52.

This relay repeats the current impulse over acontact corresponding to the contact (132 of the repeater Ue2 and belonging to the repeater U03, and transmits the impulses over the contacts an and $63 to a relay of LW5 in the exchange V corresponding to the relay R of. the final selector INVl. This relay" transfers the current impulses to the'liifting magnet of the final selector LIV5. The cir.-

cult arrangement of the final selector IAVVF) is similar to thatv 0f the final selector LVVl and ,is lillQlGfOli'O'IlOt shown in detail in the a Figure 3. After the transmission of the last impulse in the tens train of impulses,

the relayAl remains attracted for a longer time, hence the current through the winding of the relay V2 is interrupted long enough for the relay V2 to release its armature. At

the contacts e2l and 4122 the short circuit is removed from the windings of the relay A2, so that thefrelay again operates.

lVhile the calling subscriber is transmits ting the last train of impulses, the relay V2 is energized in the same manner as that def" scribed above for the tens train of impulses, J

and thusthe windlngs of the relay A2 are again short cireuited. At the final selector VR of the final selector Ill V1 is energized during the tens train of impulses and is re-' la 0 leased at the end of this t-rain,.so that the side switch is moved into position 2, thereby preparing the rotary magnet circuit. During the units train of impulses the rotary magnet is operated and positions the wipers back. The circuit of therelay V1 is inter rupted at the contact r1. Relay V1 releases and at its contact 013 closes the-circuit of the release magnet M, which has been prepared at the oit-normal contact 703. By selector LlVl is returned to its normal position in known manner. At a contact m of the re lease magnet M the marking engaged circuit of the final selector is opened, hence the relays T and O,fall back. The relay T returns the preselector VWl to its normal posltion in known manner, while the This circuit extends JAWS, a relay which corresponds to the rel y relay C, at its contact 61, interrupts the circuits of the test relay P1 and the'relay T11 01? the preselector VWT. The lead L116 is disconnected from earth at the contact 3H1, and the relay U1 of the repeater U61 falls back and opens the circuit of the relay US of the repeater U62 at the contact n12. At its contact 1511 it closes the test circuit of the line L1 for the final selector LW2, over which the line L1 can therefore now be taken into use. lVhen the relay R released, the opening of the contact 7?) caused the relay A1 to fall back. At its contact an,

it opens the circuit of the relay C1 and at the contact (012 it opens the circuit'ot the windings ot the relay A2. After a short interval, the relay G1, at its contact 615, opens the circuit of the relay V2; at the contact 613, it removes the engaged condition from the test circuit of the final selector LlV2; and it again connects the windings I and 11 of the relay A2 to battery and earth at the contacts 611 and 612. The switching means at the repeaters U62 and-U63 and the final selector Li i are returned to normal in the same manner as the repeater U61 and the final selector LWl, so tliisneed not be further described.

It a subscriber of the. exchange V, for

' example the subscriber T5, Wishes to be connected to the exchange I, the call is setup in the same manner asthat described for a call in the opposite direction. After the preselector fl V5 (Fig. 3) has found an idle final selector such as LlV5, the relays T and C8 are operated over the oft-normal contact 765 and over the test Wiperof 'VTVF). The subscriber T5 in this case dials the digit 1 to raise the Wiper or final selector LVVS to the proper level, and then dials an additional digit 1 to start the rotary trunk hunting movement. The final selector LWF) is thereby positioned on an idle trunk line for example L1. The test relay P2 is operated over the test \viper ot VVG in its normal position and over the windings oi the relay T 12. The latter, at its contacts 1t12 and 2112, disconnects the windings oi the relay R3 from the leads .63 and b3, thereby preventing the starting of the preselector VVVB and the taking into use of a final selector. At the contact 32512 the relay U6 is energized over the leadLflvcand over the contacts $61 and 6:51: there-V lay U 1 of the repeater U62 is then energized over the contact 1461 of the relay U6 and over the contact 1551. the relay U 1 being connected to the lead LlIIIc over the contacts i431 and H2. The relay U2 at. the

repeater U61 is energized over thecontacts,

n l-1. 31, the lead 111116, and overthe contacts i521 andu12; At the contacts of the relay U6 and of a relay at U63 correspondin g to therelay C4 of the repeater U62, the

lead. 62.

trunk line L1 is prevented from being taken into use by the exchange 1V. Similarly,

U62 is energized over the repeater U63,

and causes the. relay can). operate. Thus the relays A3 and A2 are connected up over the contact ($42 and the contacts. 641 and 6 12. The relay A2, at its contact 621,

closes a circuit for the relay C2, Whereupon the windings I and II of the relay A1-are bridged across the leads L116 and Tall?) over the contacts 621, a22,'and 622.

The leads L116 and LlIb are connected to the leads a2 and 62 of the preselector Vl/VT. The relay R2 is energized over its windings I andIl, and starts the preselector VVVT to hunt an idlefinal preselector in the known manner. hen the preselector leaves its normal position, its test Wiper interrupts i the testing circuit of the line L1, Which is connected to a test contact of LVVl over the An idle final selector, for example LlVl, having been found, the relay T11 oi? the preselector is operated over the lead A 65, and the Winding. of the relay C is connected to earth over the olf-norn1al contact k1; While the leads a2 and .62 are connect ed over the contacts 1t11 and 2t11. to the leads a5 and 65 going to the final selector INVl.

The number impulses are repeated in the same manner as that above described for a call in the opposite direction, so only a short description need be given here. I

Each train of impulses, repeated. by the repeatersU68 andU62, is t ansmitted by the contact 622 of the relay A2 .over the contacts 631 and 632 of the relay 1'23 and over the leads 62, 712, 65, and 7):), to the relay h.

' over its windings I and II andoverthe loop of the Wanted subscriber, thereupon inknoW n manner disconnecting the ringing current. At the end ot'the conversation the connection is released 1111311611121111181 above describedQsofit need not be further referred,

to here.

It will W er T2 Wishes to set up a. call to .a' subscriber of the exchange I. Upon liftin'gdown the rcceiver at the callingsubscribefis instrument, the preselector =VW2. is started in: known manner andhunts for an idle final selector.

be assumed that a subscriber of the exchange 11, for example the subscrih at thefinal selector LiVl. The final selector 7 LW2 for example. The first train of im- Z12 and $13 connects the leads a6 and $6 over final selector is taken into use.

prevent the trunk line L1 being taken Hill) iifl the leads Llla and LII?) tothe leadsaQ 5.2. The preselector VVVT is then started and at its test wiper opens the test lead of the line L1, so that this is marked engaged to outgoing traiiic from the exchange I, and an idle In order to use for acall from the exchanges III, IV, or V to the exchange I, the relay A]. is energized overithe contact. Z14; (earth, C21, winding II of A1, $14, winding 1 of A1, 022, battery, earth). At its contactell the re lay A1 connects up the relay C1. The latter atits contact. 013 opens the test circuit for the relays P3 and T1, but this circuit been closed in the meantime over the contact 2f15 and the resistance iVl, thus locking the relays. The relays A2 and A3 are energized in series with one another over the contacts 011 and 012. The relays C3 is operated over the contact (L31 of the relay A3, and opens at its contact 033, the test circuit of the branch of the line L1 going to the exchange I. Similarly,'the line L1 is markedengaged at the test contact of the final selector Ll Vt at the exchange IV, this being effected by switching means at the repeater U03. At the same time, a bridge is placed across the leads LlIVa and LlIVZ) at the repeater U83, corresponding to the bridge including the contact a32and the windings I and II of the relay A l atthe repeater U62. The

relay of the preselector VVVTG is thus energized and the pres-elector VIV6 is rotated oil its normal position. When the test wiper leaves its normal position, ll interrupts the test lead of the line Ll, so that the line ismarked engaged to outgoing trafiic from the exchange V. Thepositioning of the final selector LlVl and the establishment of the connection takes place in'known manner.

If the subscriber T2 wishes to set up a call to. subscriber of the exchange V, he removes his receiver and dials thenuinber ot the substation with which connectionis de-.

sired, which consists ofthe digit 5, a digit 1 to start the hunting movement and the tons and units :digits. In response toythe rcmoval of the receiver, the preelectorVVi 2 lects an idle final selector. Assuming that the final selector LIVQ is selected," its wipers are raised to-the fifth level and an idle trunk line such as L1 is found. then operated n series with the relay T2 The relay P3 over the contacts all and 024i, and connects the line of the subscriber T2 with the leads a7 and 67. The relay T2 over its contact 521, the line LlIIo and over the contacts 631 and 2A1, energizes the relay Ui-liat the repeater Ue2. As above described at its con' tact 1631, the relay U3 takes into use the re- 1 peater U 3, the preselector VVVG and a final selectorLVi ii at the exchange V. At} the contacts 622 and 623, the leads a7 and 67 are I connected to the trunk "line leads LlIIa and. LlIIb, hence the relay A3 is energized at the repeater U02 and it repcats'the current-inipuises tot-he repeater U63, which repeats the impulses to the final selector LVVS. at the ex- J.

therefore not necessary to give a description hc eof The method of operating calls over a trunk line going to one of the intermediate exchanges will now be described with reference to the Figs. 4 and 5. For this'purpose it will beassumed that a subscriber T1 of the exchange Iwishes to set up'a call to a subscriber T3 of the-exchange III. When the receiver is taken down at the instru ment of subscriber T1, the wipers of the preselector V'Wl are rotated over its bank contacts in search for an idle final selector. Assuming that the final selector Ill/V1 is the one selected, the relay T is operated in series with the relay C, when the line to this switch is reached by the wipers oi the preselector. By means of the first two trains of lH1PLll.E'GS, consisting in this case of the digit 3 andan additional digit 1 to initiate the trunk hunting movement, the

final selector is positioned on an idle trunk line in the third level, for erniinpla'trunk line L3. The relay P1 is energized over the contact Gland the lead L310 in series with the relay U7 oi the repeater U610 at the exchange II over the contact $71. The relay 2 U7, over its contact n71, the contact t72,*the

lead LZBIIO and the contact 2593, energizes the relay T8 of the repeater Uellat the exchange III. The relay T8 at its. contacts t81 and $82 switches the line section L3III incoming from the opposite direction over to the preselector VW12. At the same time, at the contact z 83 the line L3III0 is dis connected from the relay T9 and is connected to relay J2. Therelay A5 is operated whenthe'repeater UclOis taken into use. This relay, at its contact (.451, connects up the relay G5, which at its contacts 051 prepares the circuit of the relay V6. At the contacts 052 and 053 the windings I and II of the relay A9 are connected over the contact (052 across the leads L3IIa and L3IIZ). Thus, the relay A6 of the repeater U611 operates in series with the relay A9. The relay U7, at its contact 1072, interrupts the test circuit of the final selector L WQ, hence the line L3 cannot be taken into use by a subscriber of the exchange II. When the subscriber T1 transmits trains of impulses, the relay A5 falls back ateach impulse. Hence, at the first impulse a circuit is closed for the relay V6 over the contacts (051 and 051. Therelay 126 at its contacts v61 and 4162, short circuits the windings ot' the relay-A9,- thereby increasing the current flowing over the lines L3IIa and L3II6 to the relay A6 so as to improve the-transmission. It remains to be mentioned that when therelay A6 operates, its contact e61 bridges the leads a8 and 68 going over the contacts 691 and 7592 to the preselector VlVll.

The preselector VlVll is thereby started in known manner, and takes into use an idle final selector such as L NE). At each impulse, the opening of the contact (052 causes the relay A6 to fall back, thereby opening the loop which has been closed over the leads a8 and b8 and over the contacts 2591 and $92, and thus'current impulses are repeatedfor positioning the final selector LIVZS. The positioning of the final selector and the 6S? tablishment ofthe connection are effected in known manner, hence the subscriber T1 can communicate with the subscriber'T3.

If, for example, the finalselector LIVA of the exchange IV be positioned onto the same trunk line L3 by a subscriber T4, this'call can be set up independently of the connection already set up over the other section of the line I13. When the line L3 is taken into use, the. relay P5 of the final selector LWe is energized in series with the relay TR'over I the contact 1481. The relay TR applies earth to the test contact of the final selector LIV?) over the contact fir-1 and the lead LSIVG, thereby the line L3 is marked engaged tothe exchange V. At the contact 2W2, earth is applied to the lead LZBIIIO, hence the relay J 2 at the repeater U011 is operated over the contact 2583. The relay J2, at its contact j2, closes a locking circuit for the winding of the relay T8 over the contact 2585. The pur-.

pose for which this is done willbe explained hereafter. The contacts W3 and We are switched over upon the operation of the relay TB of the repeater U612 in the exchange IV.

VThe leads (110 and Z210 of the final selector LIV L are thereby connected to the leads Iii-3111a and LSIIIZ) of the trunk line. The relay A7 at the repeaterUellthen operates, and atits contact repeats the current impulses over the leads a9 and Z29 and the preselector VVV12 to a final selector such as LW3.

After the conversation between the sub scriber T1 of the exchangeI and'the subscriber T8 of the exchange III is ended, tie marking engaged circuit, extending over the lead LBIc, is interrupted, and the relay U7 falls-back The latter, at its contact 1071, opens the energizing circuit of the relay T8. Relay T8 however, does not release, because it is located in the holding circuit over the contacts and 85. Hence, the speaking or positioning circuit is maintained over the leads a9 and b9'between the exchanges IV and III until the relay J2 releases over this connection at the end of the conversation. 'I'hereupon the opening of thecontact 72 also causes the release of the relay T8.

The method will now be described for setting up a connection between the subscriber T5,'o:t the exchange V, and a subscriber of the exchange III. The pre-selector VVVS 9 hunts for an idle final selector. Assuming final selector LVV5 is the one'selected, the relay T10 is then operated over the test wiper of V W 5 in series with the relay C8 over the oil-normal contact 705. The subscribers leads are connected by way of the contacts of the relay T10 (not shown) to the speaking leads of the final selector, ,wl1-"' upon the relay'Rl isenergized over its d ings I and II. I closes a circuit for the relay V8. The trains of impulses transmitted by the subscriber T5) cause the finalselector LIV?) to be raised. to thedesired level, which in this case is the third'level, and then hunt tor an idle trunk line. Assuming that the trunk line selected is trunk line L S, the relay I 2 is energized over the contact 081, the lead LSIVc, the contact trl and through the winding of the relay US. At the contacts p51 and p52, a bridge comprising the contacts r12 and v81, is connected across the leads LSIVa and At its contact r11. rela ill:

liHl

nerve. The relay A8 is thereby operated and energizes the relay C6 over its contact e81. The opening of the contact uSlprevents the line L3 being taken into use by the exchange IV, while at the contact n82 earth is applied to the lead L3IIIO over the contact 1W2. Hence, at thev repeater Uel'l jthc relay T9 is. energized over theback contact 2583. JAt its contacts $91 and $92, the relay T9 switches the section of the line L3, incoming from the opposite direction, to the leads a9 and 69 of the preselector VVV12. At the contact e82 the windings I and II of the relay B, by way of contacts 062 and 063,"

are connected in bridge across the outgoing line L3III. The' relay. A7 at the repeater U611 is then energized. contact (671 causes the preselector VI V11 to ;The closure oi the I be started over the contacts $81 and t82 and over the leads a8 and 728. andtakes'into use an idle final selector as ll-N3. The relay A8, falls back at each impulse ofthe last two trains of impulses, Over the contact e81 reliable operation of the relay A7. The relay A8 falls back at each impulse and at its contact" e82 it opens the circuit of the relay All. The latter, at its contact (07]., opens the bridge, which has been closed over the leads at) and 28, thereby repeating thecurrent inipulses to the motor magnets ot the final selector LW3. V

Iihin the meantime, the same trunk line L3 to theexchange III has been taken into use by a subscriber T2 of the exchange 11 over his preselector vwe and thefinal selector Liiithe relays P3 and T? are enc"- gized. The relay T7 applies earth to the lead Ltllcover its contact T71, so that the trunk line taken into use appear to be marked engaged at the final or DWI. At the contacts 672 and 674:, the leads all and an are switched through to the trunk leads Lillie and L llb, while the relay J1 of the repeater U611 is energized over the contact 572, the'lead LBIIc and over the front contact 693. At the contact jl a holding circuit for the winding of the relay T9 is closed over the contact 695.

After the conversation between the sol scriher T5 and the subscriber T3 is completed, the energizing circuit tor the relay T9 is opened at the-contact n82 after therelay US has fallen back. But the relay T9 does not release, because its winding its included in the holding circuit over the contactsi1 and Not until the end of the conversation between the subscriber T2 and a subscriber of theexchange 111, does the relay T9 lali hack owing to the release of the relay J1 opening the contact yl.

It should also he mentioned that in the third lerei of the tinalflselectors shown in the First and nocalloutgoing from the hangs Ill can he set up. Therefore the of the preselector VW Sshown l dim third lev in the Fig.4 only serves :torlocal trafii within the exchange III.

The circuit arrangement of the trunlr'lines L2 Lt and L5 and of the re ieatln devices a a flSSOCltttGCl therewith correspond to those shown in the Figsr2 to '5, hence there is no need to show ordescrihe these circuits. What is claimed 1s: i

1. In a telephone system, two exchanges,

intermediate exchange, a two waytrunlr line'ccnnecting the first and. second exchanges via said intermediate exchange, automatic SWltCllGi-till the first and second exchanges for completing through connect-ions tions over said trunk line in either direction,

automatic switches in the intermediate ex-- change having access to saidtrunk line over two ditl'erent paths corresponding 7 to said first and second exchanges, respectively, and

- means effective when the trunlrline is seized bya switclrin the intermediate exchange for extending the connectionto the first or secg ond exchange depending on'the "path over which the trunk line istaken for use.

In a telephone system, two exchanges, an intermediate exchange, a two-way trunk line connecting the [first and second exchanges via intermediate exchange,

automatic switches in the firstand second exchanges for" con'ipleting through connections over said trunk li'neineither direction, automatic switchesin the intermediate exchange having access to said trunk line over two difiere11t:paths corresponding to said first and second exchanges, respectively, means efi'ectivewhen the trunlrline is seized by a switch in. the intermediate exchange for 7 extending the connection to the first or sec- 0nd exchange depending on the path over which the trunk line is taken foruse, and means for making the particular path used busy to other switches while the other path left free tor use-in con'ipleting connections over the-trunlr line to the corresponding ex change, l i

4:. In a telephone system, twofexchanges, anintermediate exchange, a twomwiy trunk line connecting the first aiul second exchar 'via said intermediate exchange, automatic"switches in the first and second exchanges for completingthrough connections over said trunk line in either direction,

automatic switchesin the intermediate exchange having access to said trunk line over two different paths corresponding to said first and second exchanges, respectively,

means efi'ective when the trunk line is seized by a switch in 'thefi'ntermediate exchange for extending the connection to the first or second exchange depending-on the path over which the trunk line is taken for use, means forllnalring the particular path used busy to other switches while the other path is lett free for use in completingconnections over the trunk line to the corresponding exchange, and means effective when the trunk line is first seized at the intermediate exchange for separating the sections. extending to the first and second exchanges, respectively, so that the section not used in the first connection can be used for the second connection without interference.

5.111 a telephone system, two end exchanges and a plurality of intermediate exchanges, a trunk line connecting said end exchanges and said intermediate exchanges in series, means for automatically establishing a talking connection from any intermediate exchange to either end exchange over said trunk line, and means for establishing a second talking connection from the same. intermediate exchange to the other of said end exchanges over said trunk line while the first connection is intact.

6. In a telephone system, two end exchanges and a plurality of intermediate ex changes, a trunk line connecting said end exchanges and said intermediate exchanges in series, means for automatically establishing a talking connection from any intermediate exchange to either end exchange over said trunk line, and means for establishing a second talking connection from said calling intermediate exchange or any other intermediate exchange not included between a calling intermediate exchange and a called end exchange to said other end exchange over said trunk line whilethe first connection is intact.

7. In a telephone system, two end exchanges and a plurality of intermediate exchanges, a trunk line connecting said end exchanges and said intermediate exchanges in series, means for automatically establishing a talking connection from any intermediate exchange to either end exchange over said trunk line, and means controlled over the two talking conductors of said trunk line in series for guarding said trunk against being taken into use by any other exchange for extending a talking connection to said called end exchange.

8. In a telephone system, two end exchanges and a plurality of intermediate exchanges, a trunk line connecting said end exchanges and said intermediate exchanges in series, means for automatically establishing a talking connection from any intermediate exchange to either end exchange over said trunk line, means controlledover the two talking conductors of said trunk line in series for guardingsaid trunk, against being taken into use by any other exchange for extendinga talking connection to said called end exchange, and means for guarding said trunk against being taken into use by any exchange included between said calling intermediate exchange andsaid called end exchange.

9. In a telephone system, two end expleting connections from any intermediate exchange to either thefirst or second end exchange or to both said firstand second ex]- changes simultaneously.

, 1 0. In a telephone system, two end exchanges, a plurality of intermediate exchanges, a two-way trunk line connecting said first and second end exchanges and said intermediate exchanges in series, automatic switches in said first andsecond end exchanges for completingthrough connections over said trunk line in either direction, automatic switches in each of the intermediate exchanges having access to said trunk. line over two different paths corresponding to said first andsecond end. exchanges, respectively, and means eifective whenlthe trunk line'is seizedby a switch in a-callinginter mediate exchange for extending the, connection to the first or second end exchange depending on the path over which the trunk line is taken for use. i Y

11. In a telephone system, two end exchanges, a plurality of intermediate exchanges, a two-way trunk lineconnecting said first and second end exchanges and said intermediate exchanges in series, automatic switches in said first and second end exchanges for completing through connections over said trunk line in either direction,automatic switches in each of the intermediate exchanges having access to said trunk line over two different paths corresponding to said first and second end exchanges, respectively, means effective when the trunk line is seized by a switch in a calling intermediate' exchange for extending the connection to the first or second end exchange dependingv on-the path over which the trunk line is taken for use, and means formaking the particular path used busy to the other switches in said calling intermediate exchange while the other path is left free for use in completing connections over the trunk linev to the corresponding end exchange; 7

12.111 a telephone system, two end exchanges, a plurality of intermediate exchanges, a two-way trunk line connecting said two end exchanges and said intermediate exchanges in series, automatic switches in said end exchanges for completing through connections over said trunk line in either direction, automatic switches in each intermediate exchange having access to said trunk line over two separate paths individual to each intermediate exchange, means effective when the trunk line 15 seized by a switch in any intermediateexchange for ex-' tending a talking connection to either one ofthe two end exchanges dependingon the path over which the trunk line is taken for use, means for preventing the seizure of said trunk by the automatic switches of the other intermediate exchanges included between a calling intermediate exchange and a called end exchange over either path, means for connecting a first and a second terminal exchange, a plurality of intermediate exchanges adaptedto extend connections over said trunk lineto either ofs'aid terminal exchanges, means at said intermediateexchanges operative upon one of said intermediate exchanges extending a call to either terminal exchange for disabling all of the remaining intermediate exchanges from extending calls in the same direction and also disabling the intermediate exchanges located between thecalling intermediate exchange and the called terminal exchange from ex tending calls to theother terminal exchange, while permitting the other intermediate ex changes not included between the calling intermediate exchange and the called terminal exchange to extend'conneetions to the non-called terminal exchange. a I

14. In a telephone system, a first and second trunk linenormally connectedtoa first automatic switch and; normally disconnected from a second automatic switch, and means for disconnecting either of said trunk lines from the first said automatic switch and connecting it to the second automatic switch when the first of said automatic switches is taken for use over thexother of said trunk lines. a 15. In a telephone system, exchange, atrunk line extending through said exchange, automatic switches in said exchange having access to said trunk over either of two paths depending on the digit dialled, and means forextendlng a call in either direction over said trunk line from said exchangedepending on which path said trunk line is seizedover.

16. In a telephone system, an automatic exchange, a trunk line extending through an automatic said exchange, automatic switches in said'exchange having access to said trunk over either of two paths depending on the digit dialled, means for extending a call in either direction over said trunk line from said exchange depending on which path said trunk line is seized over, andmeans for making the particular path busy to other switches in said exchange While the other pathis left free for use in completing calls over said trunk line in the other direction; 7, 1 17. In a telephone system, an automatic exchange, a trunk line extending through said exchange, automatic switches in said exchange having access to said trunkover either of two paths depending on the digit dialled, meansfor extending a call in either direction over said trunk line from said :exchange depending on which :pathsaid trunk line :is. seized over, means for imakingqithe particular path busy to other switches in 'said exchange while the other, pathwi s left freefonuse in completing callsover said trunk linein the other direction, and "means effective when the trunk line is' first seized for separating the trunk into two sectionsfirst trunk line to the first automatic switch.

19. In a telephone system, a first and a second trunkline normally connected to a first automatic switch andnormally di'sconr nected from a second automatic switch, and means for disconnectingthe secondtrunk line from the first automatic switch andlfor connecting it to the second automatic switch when a connection is established-over the first trunk line to the first-automatic switch, and means for maintaining the secondgtlfunk line connected to the second automatic switchafter the termination of the connection over thefirst trunk line when a connection is established over the secondtr-unk line to the second automatic switch.

20. In a telephone system, two end exchanges, an intermediate exchange,:'a trunk line comprising talkingconductors and arelease conductor connecting said end exchanges and said intermediate exchange in series, means for automatically establishing a connection fromsaid intermediate exchange to either endexchangeover' said trunk line, means for automaticallyestab lishing a connection from one of said en'dex changes to the other over said trunk line,

means operable when said second connection is established and controlled over the tWo talking conductors of said trunk line in series for preventing the taking into use of 5 said trunk line at said intermediate exchange for establishing a connection to the calling end exchange, and means controlled over the release conductor of said trunk line for preventing the taking into use of said trunk line at said intermediate exchange for establishing a connection to the called end exchange. In Witness whereof, I hereunto subscribe my name this 20th day of July, A. D. 1925.

ALEXANDER BRUNO PREUSS. 

